I think your last sentence is important - you were already gone, it was just a matter of time. If the numbers work such that losing 1% of customers means keepi

I think your last sentence is important - you were already gone, it was just a matter of time. If the numbers work such that losing 1% of customers means keeping 3% i.e. the email prompts them to leave/stay respectively, then it's worth sending. Getting rid of low-value users - in this case those not playing - can have long term benefits of focusing the business on getting more custom instead of getting comfortable on revenue that may disappear at any point.